Battery control circuit



y 1933- w. H. T. HOLDEN BATTERY CONTROL CIRCUIT Filed March 17, 1930 INVENTOR WflZZbZden/ yQ-/%- ATTORNEY Patented July 4, 1933 UNITED STATES WILLIAM H. T. HOLDEN, 0F BRGOKLYN, NEW YORK, ASSIGNOR TO AMERICAN TELE A'rENT OFFICE PHONE AND TELEGRAPH COIvIPANY, A CQRPOILATION OF NEVT YORK BATTERY CONTROL CIRCUIT Application filed March 17, 1930. Serial No. 436,545.

This invention relates to circuits and apparatus for producing substantially constant direct current voltages. More particularly, this invention relates to control circuits and apparatus for a storage battery whereby abrupt changes in the voltage at the beginning and end of charge and discharge may be eliminated.

This invention will be described in connec tion with the accompanying drawing showing one embodiment thereof merely for the purpose of illustration.

Referring to the drawing, reference character O designates a source of three-phase alternating current of any frequency which may be, for example, 60 cycles per second. A triple-pole single-throw switch S may be operated to connect this source with the field windings of a motor M which is mechanically coupled to a generator G Another triple-pole single-throw switch S may be similarly operated to connect the source 0 with the field windings TV of a motor M5 which is mechanically coupled to a generator G The armature of the generator Gr is shunted by a field winding L and a rheostat R which are connected in series relationship. The armature of the generator G is shunted by a similar arrangement including a field winding L and a rheostat R The rheostats R and R may be manipulated in order to control the voltages derived from generators G and G respectively.

Circuit breakers K, and K are associated with the generators G and G respectively. The circuit breaker K includes two windings L and L,, which are in inductive relationship. lVinding L is connected in shunt with the armature of the generator G while winding L is in series with the armature of this generator. These windings produce similarly poled magnetic fields while the generator G is supplying current to its connected circuits, yet when the direction of the current is reversed, the magnetic fields of these windings become mutually opposite, operating an armature or other movable element so as to break the circuit. The circuit breaker K includes similar mutually reactive windings L and L which function in the same manner as windings L and L just described. Thus, as current begins to flow into either of the generators G or G the associated circuit breaker will operate so as to open the circuit in order to prevent the destruction of the generator armature.

Thereference character B designates a battery of secondary cells or other sources of electromotive force, and this may be a storage battery each of the cells of which may include a plurality of lead plates immersed in a solution of sulphuric acid, as is well known in the art. 'The reference character X will be employed to represent the number of cells forming battery B A battery B is composed of a plurality of sources of counter-electromotive force, each of which consists of two or more electrodes, which may be of nickel, immersed in a fluid conductor, which may be an alkaline solution. The reference character Y'will be employed to designate the number of cells forming battery B Before proceeding with the specification, it may be well to compare the properties of each of the cells of battery B with each of those of battery B Current may only pass between the electrodes of each of the cells of battery B upon decomposition of the electrolyte into ions. This current cannot be established until the electromotive force impressed across the terminals of the cell is sufficient to perform the work of decomposition, and a current having a smaller electromotive force than that required to perform such work (the latter being termed the critic'al voltage) cannot be transmitted through v ductor, or by changing the spacing of the electrodes. The difference between each cell of counter-electromotive force of battery B and each secondary cell of battery B isth at,

while the former is able to ofler the counterand maintaining.

: Itisinterestinghere to note bl-1Hb'WlIEIL1tlIQ.

Proceeding now with the specification, it will be seen that the upper terminal of a rheostat R is connected to the lower terminal of the battery B while the other terminal of: therheostat is connected to-one otthe'bladesof a double+pole single-throw: switch sgv The-other blade-of the switch S isconneotedtothe movable arm=of the rheostat- R The remaining two terminals of the switch S are connected tothe out-er ter-- minals of the battery B So, it Wlll bBFSQGII that wheirthe switch S is-open, ther-heostat R rwill be in 'series withbatteriesB and B and that when it is closed, rheostat- R will i be in'shunt withthebattery 13 1..

An output circuit-1O- ;is connected between the variable arm of: therheostat. B and the upper terminalv of the batteryB through a:

filter F which is of the'low -pass type and includes equal series inductances and: equal shunt capacitive elements; The output circuit-O isshunted by a1 voltmeter V A similar voltmeter is connected in shunt witli'the batteryB Oneside oftheoutput circuit 0 may be grounded, asshown:

A trickle-charger D, of; any well knowntype, is connected between: two of the conductors leading to the source 0 and the battery B The current supplied: normally by. the trickle-charger: D has an amplitude; of between one-half and one pe'r: cent; of the eight-hourcharging. rate of the-battery B A currentofi this amplitude will compensate for the lossesinthe cells of the'battery B ,re--

sulting from local: action, leakage-and self discharge.

. A=switch S unaybe operated for thepur pose of connecting. the generator Gi inserieswith batteries B andrB l through the circuit breaker K A similar SWitOl1 S :l1llly1 be operated to connect the" generator G with the battery B through the circuit breaker 2-" The number of secondary cells requiredfor. battery B may be deterinined from the voltage assigned to the output circuit 0g and from the Voltage of= each ofthesecells when it is completely discharged. Ifit be assumedthat each" secondary cell is completely dischargedwhenits-termin alvoltage is about'lflfi volts,- the number of cells re quired may beroughly obtained by dividing thevoltage assigned to the circuit-O by 1.75.

battery B is being properly floated under normal conditions, each cell will exhibit about 2.15 volts, and that each cell may exhibit approximately 2.6 volts or more when it is fully charged and the charging current is flowing. V

Each of the cells of counter-electromotlve force of battery B presents a large resistance when the impressed voltage per cell is lessthan-the criticalvoltage (1.75 volts per cell); If the voltage of thegenerator Gr becomes greater than the voltage of the battery B by an amount which is less than the value obtained by multiplying the critical voltage of each cell (1.75 volts) forming battery'B 'andaY, which represents the number of? cells in battery B then substantially nocur nentwillflow from battery B into the out put circuit 0 nor" will current flow: from generator G into battery, B In that case the voltage across the output circult @3115" indicated: by the voltmeter V will be approximately equal to the voltage producedby generator G armature of. the generatorGr is unable to ro tate, switch S being open and the movable arm-of rheostat'l'hl being atlts uppermost position, thevoltage across the outputcircuit. 0 5, as indicated by the voltmeter V will'be' reduced to that voltage'correspondlngto the:-

diiferencein the voltage drops across batteries B and'E Upon the closure of switch S therheostat R willbe connected in par allel with the battery B and the voltage V at the output circuit Ogmay be maintained constant'by controlling:the rheostat R As soon as the potential drop across the rheostat: becomes less thansthe'critical voltage ofbattery B practically all of the current will flow through the rhcostat-and' the voltage at the output circuit O willbe approximately equal: to'the differencebetweenthe voltage of bat}.

tery B and the drop in voltage across'the rheostat, through which practically all of the current transmitted to circuit willflown It will be necessary to gradually reduce the resistance of the rheostat R asthe battery B discharges, and at full: discharge all of the resistance of the rheostat R Willbecut out.

The rheostat R should include resistance of such a value that when all of its resistance-is connect'edacross the battery 13 under normal conditions, the potential dropacross the rheostat willbe somewhat greater than the critical voltage of the battery B Ifthe voltage'drop across therheostat under theseconditions exceeds, for example, the value 1.75Y volts, the rheostat will then be properly designed, and; when the switch S is'cl'osedupon-the discharge of battery B only a part, of thecurrent trombatteryB will 'flow;

through the-rheostat. It will beapparent that it the switch S isclosed; immediately lVlien' the power service fails-so that the l'IO I upon the discharge of battery B proper manipulation of the rheostat R will prevent any appreciable variation in the voltage across the circuit 0 \Vhen the power service is restored, the switches S and S may be closed so that the e'itects of generators G and G may be re spectively impressed upon the attached cir cuits. In that event, the switch S may at first be maintained closed and the rheostat increased in resistance until the voltage across battery B as indicated by the voltmeter V is greater than the value attained by multiplying 2.15 by X, the number of cells in battery B Further increase in the voltage of the battery B beyond the value just determined will cause current to flow from generator G into the output circuit 0 because the difference between the voltages of batteries B and B will be substantially greater than the voltage assigned to the output circuit 0 This may be overcome by increa ing the voltage of generator G which, of course, may be accomplished by the adjustment of the rheostat R The voltage of generator G should be so large as to maintain the voltage drop across battery B below the critical value.

In order to prevent the voltage of the output circuit O from increasing too'greatly, the switch s may be opened so as to connect the rheostat R in series with batteries B and B and with the circuit 0 The resistance of the rheostat R may then gradually be increased in order to maintain the volt age V across the output circuit 0 substantially at the assigned value.

hen the battery B becomes fully charged, at which time the voltage V will be greater than the product of and X, then the switch S may be opened so as to disconnect the charging generator G from the battery B The trickle-charger D will continue to supply current to the battery E the voltage of which will then slowly drop tothe normal floating voltage of 2.15 volts per cell. The voltage of the floating generator G may then be gradually reduced and the resistance of the rheostat R also gradually reduced until all of its resistance has been cut out. It is to be noted that the generator G should be able to produce a voltage somewhat higher than that of the floating. generator G and the generator G should be able to charge battery B at the normal eighthour rate.

It will be apparent that the generator G is arranged to supply current to the output circuit 0 under ordinary conditions and that this generator, while connected across batteries B and B runs as long as power is available at the input circuit O The generator G will ordinarily remain unoperated, the switches S and S being normally open, and the trickle-charger D will continually supply the usual energy losses encountered by battery B which remains idle particularly because its voltage is less than the voltage V of the output circuit 0 However, after a power failure has occurred and service has been subsequently restored, the battery B be accomplished by reducing the magnitude of the resistance R Furthermore, the voltage of the generator Gr must not be raised so high as to be greater than the additive values of the normal charging voltage of the ba tery B and the critical voltage of'the bat tery B (1.75 Y) for if this value should be exceeded, current will flow from the gen erator G into the battery B and the generator G will become overloaded. At the same time the voltage of the battery B will have risen to its normal charging voltage, and the voltage of this bat-tery, which is V will be greater than the voltage at the output circuit 0 if the generator G is not increased. in voltage as above described. Current may then also flow from the battery B through the battery B to the generator G and therefore the circuit-breaker K will be operated. to disconnect the generator G from its associated circuits. The generator G will is then supply the entire load to the output circuit 0 as well as the current required to charge the battery B It will be apparent that the battery control circuit shown and described in this application permits the voltage at the output circuit 0 to be maintained highly constant at some predetermined value while the main battery B is being either charged or discharged.

The filter F is employed for the purpose of suppressing alternating currents which may be superimposed upon and introduced into the system due to commutator ripples, etc., from generators G and This filter may have a cut-off frequency of, for example, 70

or 80 cycles. It is also to be noted that this filter will present crosstalk in the output circuit 0 which may occur because of the common impedance presented by the rheostat R It will be understood that while this invention has been shown in one particular embodiment merely for the purpose of illustration, the general principles of this invention may be applied to other and widely varied organizations without departing from bination of a plurality of secondary sources of electro'moti've force connected "in series with each other, a plurality of sources of counter-electromotive force connected in series with each other and with said secondary sources, the :series'circuit of said sources being "connected in shunt with the input and output circuits, a variable resistance, means for "connecting saidresistance in series with all of said sources and :in series with said output circuit, and means ifor connecting said resistance in parallel with all of the sources 'o'f counter-electromotive force.

2. The combination of a storage battery, a :battery "of cells of 'counter-electrcinotive force, a first direct current generator connected to said storage battery, "and 1 a second direct current gei'ieratorconnected in series with both batteries. V

'3. The combination of a first battery of secondarycells, a second battery of cells of 'counter-electromotive force, a first direct current generator connected to the storage battery, a second -direct *current generator connected in series with both batt'eries, and atriclile-charger also connected to said stor- =age battery.

*4. The combination of a source of alterna'ting current, first and second'inotor generator sets connected :in' parallel "with said sourceya storage battery, a battery of cells of counter=clectro1notiyeforce connected in series with said storage battery, a tricklecharger coupled 'to said alternating current source,the generator of the lirst set and said tri'c kle-charger being connected in parallel with i said storage battery, the generator of the second set being connected in series with bothbatteries.

5. The combination of a source of alternating current, first and second generators operated from said source, a storagebattery, abattery of counter-electromotive "force cells in series withsa'idstorage battery, anoutput circuit-connected across both batteries, and a tricklecharger coupled to the alternating current source, the first generator and the trickle-charger being connected in parallel with the storage battery, the secondtgen'er- *ator'beingconnected across the output cirsuit.

6. Ina battery control system, a load circuit'to be'su'pp lie d with current, a battery, counter electromotive force cells in series a i9 1 c ,3116

arratngement with I-said battery and across said load circuit, a rheostat, and manual means forconnecting said rheostatin parallel with said counter-electromotive force cells or inrseries withsaidload circuit.

7. fI- n asy-stem for supplying current to a translating circuit, the combination of a secondary battery, a battery of counter cells, said batteries being connected in series with eacli otheran'd in shunt with the translating circuit, and a rheostat connected in shunt across said *batteryofcounter cells.

=8. =In a system for supplying current'to a translating "circuit, the combination of a storage battery, a battery of counter cells connected in series with the storage battery, said series batteries'being connected in shunt with the translating circuit, a rheostat, and means iorconnecting said rheostat :in shunt with said battery of counter cells or in series with said translating circuit.

1 '9. The combination of a source of'direct current,a translatingcircuit, a storage battery connected in shunt with said source of direct current, a battery of counter cells, said batteries being connected 'in series with each other and in shunt with-said translating circuit, and a rheostat connected in shunt "with the battery 20f counter cells.

10;Ina system for supplying current to a translatingcircuit, the combination of a storagebatteryya battery of counter cells, a generator connected in series with both'the storage battery and the battery of counter cells, said igenerator being also connected across'the translating circuit, andarheostat connected in shunt'with'thebattery of counter cells.

' 11. :Apparatus for connection across an input circuit'and an output circuit which is -to be supplied with current from said input circuit comprising, in combination, a source of direct current potential, a battery of'countercells'connected'in series with said source of direct'current potential, and a rheostat'connected in shunt with said battery'ofcounter cells and having a resistance which will normally produce a Voltage dropgreater than the critical'voltage'of said battery of counter cells.

In testimony whereof, I have signed my name to this specification :this 15th day of 'March, 1930.

WILLIAM H. T. HOLDEN. 

